Vernalization Duration and Light Intensity Influence Flowering of Three Hybrid Nobile Dendrobium Cultivars

Abstract

The flowering time and flower quality of three hybrid Dendrobium nobile cultivars in relation to light intensity during cooling and duration of vernalization were studied in the first experiment. Mature Dendrobium Red Emperor 'Prince', Den. Sea Mary 'Snow King', and Den. Love Memory 'Fizz' plants were vernalized at 10 °C under 300 to 350 μmol m-2 s-1 photosynthetic photon flux (PPF) (12-h photoperiod) or darkness, each with four cooling durations (2, 4, 6, or 8 weeks). Plants were forced in a greenhouse after vernalization. At least 4 weeks of 10 °C cooling in light was needed for complete flower initiation of Den. Red Emperor 'Prince', whereas Den. Sea Mary 'Snow King' and Den. Love Memory 'Fizz' only needed 2 weeks of 10 °C cooling regardless of light. For all three cultivars, darkness during vernalization slightly delayed flowering and resulted in fewer but larger flowers. Longer cooling duration delayed flowering, decreased flower longevity, and produced more and larger flowers. In a second experiment, Den. Love Memory 'Fizz' plants were vernalized at 15 °C for 4 weeks under a 12-h photoperiod and PPF of 0, 50, 100, or 200 μmol m-2 s-1. Compared with 200 μmol m-2 s-1, low PPF at 50 or 100 μmol m-2 s-1 did not affect flowering time or flower qualities; however, darkness delayed flowering and reduced flower qualities except flower diameter.